Tanning for the production of leathers of various kinds



I Patented Mar. 15, 1932 UNITED STATES PATENT OFFICE HERBERT TRbG-ER, F PLAUEN, GERMANY No Drawing. Application filed July 28, 1927, Serial No. 209,158, and in Germany February 24, 1926.

My invention relates to the art of tanning hides and skins. I

Its object is toprovide new and efiicient means for reducing the time required for the tanning processes and for improving at the same time the quality of the tanned products so as to obtain only uniformly and thoroughly tanned leathers which are soft and impervious to water.

' According to my invention, fermenting organisms are added to the tanning liquor; the tanning liquor containing the hides to be treated is alternately subjected to pressure and to vacuum in sequence and, moreover, the

1 hides are subjected to the action of an electric current during the tanning operation.

The firststep above-mentioned is carried out by inoculating "the tanning liquor with yeast, such as brewers yeast, or bacteria adapted to support andstimulate fermentation said bacteria may be raised on organic or inorganic substances such as wheat-glutenstarch, sodium-thiosulphate (Na S O etc. The above-mentioned fermenting agents are preferably added progressively in small doses to the tanning liquor while being made viz. before the liquor is used for tanning or else may be added during the tanning process proper.

The total quantity of the fermenting agents to be added may vary to from 0.25% to 35% of the weight of the liquor consistent with the concentration and fermenting efiiciency of the respective agent, and the depletion of the tanning-liquor during .the tanmng'process is compensated by adding ground tanning substances. j After the raw depilated hides or skins have been placed in the tanning vessel-preferably hung up on ropes or chains in-the latterthe air 1s pumped out of the vessel and the tanning liquor, mixed with stimulating agents as above set forth, is subsequentl admitted into the vessel, while the latter is ept under vacuum. 4 After the liquor has been allowed sufiicient time to impre ate the material under treatment air is a itted into the tanning vessel and is compressed therein to a pressure of sevv eral'atmospheres. The contents of the vessel to claim 2, in which steam is introduced into tion.

are then alternately subjected to a vacuum and to air pressure in sequence until the tanning is completed.

During the tanning operation, the hides and skins suspended in the bath are subjected to the action of an electric current.

Direct or alternating current may be used for this purpose at a ressure of about 20-35 volt consistent with t 1e size of the tanningvessel. Voltage and amperage of the current 60 may of course be varied according to circumstances. The current is led to the bath b electrodes which are preferably made of har lead, alloyed with antimony, or other substances adapted to stand the chemical attacks of the tanning liquor and their admixtures.

The tanning operation may be carried out either in revolving drums or in stationary drums or containers. Steam may advaning the tanning operation.

What I claim is:

' 1. A method for tanning hides which consists in suspending the hides in a tanning liquor inoculated with fermentation organisms, creating in the tanning container pressure alternately below and aboveatmospheric pressure, and causing an electric current to flow through the tanning liquor during the tageously be introduced into the liquor, durtanning operation. w

2. A method for tanning hides and skins which consists in suspending the hides in a tanning liquor containing fermentation organisms, creating in the tanning container pressures alternately below and above atmospheric pressure, and causing an electric ourrent to flow through the tanning liquor during the tanning operation.

3. A method for tanning hides according no the tanning liquor duringthe tanning opera- "In testimony whereof I have signed my name to this specification.

- HERBERT TRoGER. 

